scholarly journals Climate variability in West Antarctica derived from annual accumulation-rate records from ITASE firn/ice cores

2004 ◽  
Vol 39 ◽  
pp. 585-594 ◽  
Author(s):  
Susan Kaspari ◽  
Paul A. Mayewski ◽  
Daniel A. Dixon ◽  
Vandy Blue Spikes ◽  
Sharon B. Sneed ◽  
...  
Keyword(s):  
Climate Variability ◽  
Moisture Transport ◽  
Southern Oscillation ◽  
Accumulation Rate ◽  
Drainage System ◽  
Ice Cores ◽  
Cyclonic Activity ◽  
West Antarctica ◽  
Sea Level Pressure

AbstractThirteen annually resolved accumulation-rate records covering the last ~200 years from the Pine Island–Thwaites and Ross drainage systems and the South Pole are used to examine climate variability over West Antarctica. Accumulation is controlled spatially by the topography of the ice sheet, and temporally by changes in moisture transport and cyclonic activity. A comparison of mean accumulation since 1970 at each site to the long-term mean indicates an increase in accumulation for sites located in the western sector of the Pine Island–Thwaites drainage system. Accumulation is negatively associated with the Southern Oscillation Index (SOI) for sites near the ice divide, and periods of sustained negative SOI (1940–42, 1991–95) correspond to above-mean accumulation at most sites. Correlations of the accumulation-rate records with sea-level pressure (SLP) and the SOI suggest that accumulation near the ice divide and in the Ross drainage system may be associated with the mid-latitudes. The post-1970 increase in accumulation coupled with strong SLP–accumulation-rate correlations near the coast suggests recent intensification of cyclonic activity in the Pine Island– Thwaites drainage system.

scholarly journals The easternmost tropical Pacific. Part II: Seasonal and intraseasonal modes of atmospheric variability

2016 ◽  
Vol 64 (1) ◽  
pp. 23 ◽  
Author(s):  
Jorge A. Amador ◽  
A. M. Durán-Quesada ◽  
E. R. Rivera ◽  
G. Mora ◽  
F. Sáenz ◽  
...  
Keyword(s):  
Climate Variability ◽  
Moisture Transport ◽  
Southern Oscillation ◽  
Tropical Pacific ◽  
Transport Processes ◽  
Seasonal Migration ◽  
World Heritage Site ◽  
Summer Drought ◽  
Low Level ◽  
The Caribbean

<p>This is Part II of a two-part review about climate and climate variability focused on the Eastern Tropical Pacific (ETP) and the Caribbean Sea (CS). Both parts are aimed at providing oceanographers, marine biologists, and other ocean scientists, a guiding base for ocean-atmosphere interaction processes affecting the CS, the ETP, and the waters of Isla del Coco. Isla del Coco National Park is a Costa Rican World Heritage site. Part I analyzed the mean fields for both basins and a larger region covering 25º S - 35º N, 20º W - 130º W. Here we focus on a smaller area (65º W - 95º W, 0º - 20º N), as a complement to Part 1. Incoming solar radiation and surface energy fluxes reveal the complex nature of the ETP and CS for convective activity and precipitation on seasonal and intraseasonal time scales. Both regions are relevant as sources of evaporation and the associated moisture transport processes. The American Monsoon System influences the climate and climate variability of the ETP and CS, however, the precise way systems affect regional precipitation and transport of moisture, within the Intra Americas Sea (IAS) are not clear. Although the Caribbean Low-Level Jet (CLLJ) is known to act as a conveyor belt for moisture transport, intraseasonal and seasonal modes of the CLLJ and their interactions with other IAS systems, have to be further investigated. Trans-isthmic jets, exert a variable seasonal wind stress force over the ocean surface co-generating regions of great marine productivity. Isolated convection, the seasonal migration of the Intertropical Convergence Zone, the hurricane season, the Mid-Summer Drought, the seasonal and intraseasonal behavior of low-level jets and their interactions with transients, and the southward incursion of cold fronts contribute to regional seasonal precipitation. Many large-scale systems, such as El Niño-Southern Oscillation, the Atlantic Multidecadal Oscillation and the Madden-Julian Oscillation (MJO, also influence the variability of precipitation by modulating regional features associated with convection and precipitation. Monthly tropical storm (TS) activity in the CS and ETP basins is restricted to the period May-November, with very few cases in December. The CS presents TS peak activity during August, as well as for the number of hurricanes and major hurricanes, in contrast to the ETP that shows the same features during September.</p><div> </div>

Comparison of isotopic signatures in ice core and speleothem records to an isotope enabled climate model simulation for the last millennium

2021 ◽  
Author(s):  
Yannick Heiser ◽  
Janica Bühler ◽  
Mathieu Casado ◽  
Kira Rehfeld
Keyword(s):  
Climate Variability ◽  
Climate Model ◽  
Southern Oscillation ◽  
Ice Core ◽  
Ice Cores ◽  
Isotope Ratios ◽  
Last Millennium ◽  
Polar Ice ◽  
Geophysical Research ◽  
Ice Core Records

&lt;div&gt; &lt;div&gt; &lt;div&gt; &lt;p&gt;Stable water isotope ratios (&amp;#948;18O) measured in e.g. ice-cores or speleothems have long been established as temperature proxies and are used to reconstruct past climate variability but still require more quantification on spatial and temporal scales. The high resolution ice-core archives are mainly found in polar and alpine regions, whereas the speleothem records mostly grow in caves in low to mid-latitudes. To bridge between the archives, models are needed to compare the climate variability stored in both ice-cores and speleothems, which will help to evaluate future projections of climate variability.&lt;/p&gt; &lt;p&gt;Here, we compare a transient isotope enabled simulation from the Hadley Center Climate Model version 3 (iHadCM3) [1, 2] to polar ice-core records from the iso2k database [3] for the last millennium (LM, 850-1850 CE). We analyze time-averaged isotope ratios and their variability on decadal to centennial timescales to systematically evaluate the offsets and correlation patterns between simulated and recorded isotopes to specific climatic drivers. For better comparability between speleothem and ice core-archives, we also include non-polar ice core records, as well as monitored precipitation &amp;#948;18O from a global database.&lt;/p&gt; &lt;p&gt;We find the time-averaged &amp;#948;18O offsets between the simulation and ice-core records to be fairly small for most of the polar ice-core sites, indicating a low simulation climate offset.&lt;br&gt;As expected, we find the simulated &amp;#948;18O variability to be higher in the polar regions of ice-core locations, compared to the simulated variability at speleothem cave locations. Recorded &amp;#948;18O variability is also generally higher as stored in ice-cores, compared to that stored in speleothems. Both speleothems and ice-core records show damping effects on decadal time scales, which can in part be attributed to the temporal resolution of the individual records. This comparison of different proxy archives to isotope-enabled GCM output shows a promising way to evaluate the model&amp;#8217;s capability to resolve &amp;#948;18O variability.&lt;/p&gt; &lt;div&gt; &lt;div&gt; &lt;div&gt; &lt;p&gt;[1] &amp;#160;B&amp;#252;hler, J. C. et al. Comparison of the oxygen isotope signatures in speleothem records and iHadCM3 model simulations for the last millennium. Climate of the Past: Discussions 1&amp;#8211;30 (2020).&lt;/p&gt; &lt;p&gt;[2] &amp;#160;Tindall, J. C., Valdes, P. J. &amp; Sime, L. C. Stable water isotopes in HadCM3: Isotopic signature of El Ni&amp;#241;o-Southern Oscillation and the tropical amount effect. Journal of Geophysical Research Atmospheres 114, 1&amp;#8211;12 (2009).&lt;/p&gt; &lt;p&gt;[3] Konecky, B. L. et al. The Iso2k database: A global compilation of paleo-&amp;#948;18O and &amp;#948;2H records to aid understanding of Common Era climate. Earth System Science Data 12, 2261&amp;#8211;2288 (2020).&lt;/p&gt; &lt;/div&gt; &lt;/div&gt; &lt;/div&gt; &lt;/div&gt; &lt;/div&gt; &lt;/div&gt;

Weihe Basin Drilling Project (WBDP): Cenozoic tectonic-monsoon interactions

2020 ◽  
Author(s):  
Zhisheng An ◽  
Peter Molnar ◽  
Peizhen Zhang ◽  
Hendrik Vogel ◽  
Mark Level ◽  
...  
Keyword(s):  
Climate Variability ◽  
Ice Cores ◽  
The Arctic ◽  
Second Phase ◽  
The Tibetan Plateau ◽  
Sedimentary Record ◽  
Weihe Basin ◽  
Drilling Project ◽  
Millennial Scale

&lt;p&gt;Earth&amp;#8217;s climate underwent dramatic cooling throughout much of the Cenozoic, which has been linked to continental drift, mountain building, and the formation and expansion of ice-sheets in Antarctica and the Arctic. In particular, the India-Asia collision and uplift of the Tibetan Plateau (TP) have been posited as critical events responsible for increasing the rates of physical and chemical weathering on land, thereby decreasing the CO2 concentration of the atmosphere. The uplift of the TP ultimately led to the onset of the complexly coupled monsoon-arid environmental system in East Asia. Global-scale studies of Cenozoic deep-sea sediments and Quaternary ice cores indicate that, superimposed to the long-term cooling trend, climate variability at orbital-to-centennial time-scales is primarily induced by changing solar insolation and irradiance, and strongly modulated by complex internal land-air-ocean interactions. From the continental perspective, however, both the dynamics and impacts of long-term climate evolution and short-term climate variability remain poorly constrained due to the paucity of continuous terrestrial sequences spanning the entire Cenozoic.&lt;br&gt;The Weihe Basin is located in the monsoon-sensitive region to the north of the Qinling Mountains, a landform that constitutes the geographic and climatic boundary between northern and southern China. In the depocentre of this basin, a predominantly lacustrine sedimentary sequence with a thickness of &gt;7 km, provides an unprecedented opportunity for: (1) reconstructing tectonic-to-millennial-scale climate changes from the Eocene to the present; (2) elucidating basin-mountain coupling processes; (3) assessing the effects of Cenozoic tectonic-climate interactions on the onset and evolution of the Asian paleomonsoon; and (4) investigating climatic/environmental impacts on the evolution of microbial communities. Importantly also, (5) sedimentary filling of the Weihe Basin can potentially yield unique high-resolution records of continental climate variability during high atmospheric CO2 periods of the Eocene, mid-Miocene, and Late Pliocene, and thus serve an analog for Earth&amp;#8217;s near future climate.&lt;br&gt;The Weihe Basin Drilling Project (WBDP) proposes a two-phase drilling strategy to recover a complete as possible Cenozoic terrestrial sedimentary record from the eastern Weihe Basin depocenter. In the first phase (applied for here) we aim at producing a 3-km-long pilot sedimentary record (WBDP-1) to test the best suitable analytical approach and to reconstruct orbital-to-millennial-scale climate variability since the Late Miocene. In the second phase our aim is to produce a 7.5-km-long sedimentary record (WBDP-2) spanning the entire Cenozoic sedimentary infill of the Weihe Basin. The regional geological framework is well characterized through numerous exploration boreholes and detailed multichannel seismic reflection surveys. Scientific drilling operations will be accompanied by downhole logging, as well as on- and off-site analyses of the retrieved cores. The WBDP-1 borehole is expected to yield a world-class paleoclimate record for the last ~10 Ma and lead to fundamental advances in our understanding of multi-timescale climate variability and tectonic-climate monsoon linkages. The project will also enhance public awareness of human adaptation to Earth&amp;#8217;s changing environment.&lt;/p&gt;

scholarly journals Effect of climate variability on event frequency of sorghum ergot in Australia

2003 ◽  
Vol 54 (6) ◽  
pp. 599 ◽  
Author(s):  
Enli Wang ◽  
Malcolm Ryley ◽  
Holger Meinke
Keyword(s):  
Climate Variability ◽  
Southern Oscillation ◽  
Climatic Conditions ◽  
Considerable Research ◽  
Significant Difference ◽  
Negative Effect ◽  
Claviceps Africana ◽  
Relative Risk Assessment ◽  
Resistant Genotypes

The significant effect of ergot, caused by Claviceps africana, on the Australian sorghum industry, has led to considerable research on the identification of resistant genotypes and on the climatic conditions that are conducive to ergot outbreaks. Here we show that the potential number of monthly ergot events differs strongly from year to year in accordance with ENSO (El Niño–Southern Oscillation)-related climate variability. The analysis is based on long-term weather records from 50 locations throughout the sorghum-growing areas of Australia and predicts the potential number of monthly ergot events based on phases of the Southern Oscillation Index (SOI). For a given location, we found a significant difference in the number of potential ergot events based on SOI phases in the preceding month, with a consistently positive SOI phase providing the greatest risk for the occurrence of ergot for most months and locations. This analysis provides a relative risk assessment for ergot outbreaks based on location and prevailing climatic conditions, thereby assisting in responsive decision-making to reduce the negative effect of sorghum ergot.

scholarly journals Natural Climate Variability During the Holocene

Radiocarbon ◽  
2007 ◽  
Vol 49 (2) ◽  
pp. 837-854 ◽  
Author(s):  
V A Dergachev ◽  
O M Raspopov ◽  
F Damblon ◽  
H Jungner ◽  
G I Zaitseva
Keyword(s):  
Time Series ◽  
Climate Variability ◽  
Ice Cores ◽  
Cosmogenic Isotope ◽  
Radiocarbon Age ◽  
Earth’S Climate ◽  
Climatic Time Series ◽  
Natural Climate ◽  
Isotope Content

High-precision radiocarbon age calibration for different terrestrial samples allows us to establish accurate boundaries for many climatic time series. At the same time, the fluctuations of 14C content reflect solar variability. A bispectrum analysis of long-term series of the 14C content deduced from decadal measurements in tree rings demonstrates the existence of amplitude modulation, with a period of main modulation of ∼2400 yr. In 14C time series for the last 11 kyr, major oscillations are distinguished at 8.5–7.8, 5.4–4.7, 2.6–2.2, and 1.1–0.4 cal kyr BP with ∼2400-yr periodicity. High amplitudes in cosmogenic isotope content with a periodicity of about 2400 yr appear synchronous to cooling events documented in Greenland ice cores, to the timing of worldwide Holocene glacier expansion, and to the periods of lake-level changes. This paper focuses on revealing solar forcing on the Earth's climate and about the nature, significance, and impact of sharp Holocene climate variability on human societies and civilizations.

Holocene Climate Variability in Antarctica Based on 11 Ice-Core Isotopic Records

2000 ◽  
Vol 54 (3) ◽  
pp. 348-358 ◽  
Author(s):  
Valérie Masson ◽  
Françoise Vimeux ◽  
Jean Jouzel ◽  
Vin Morgan ◽  
Marc Delmotte ◽  
...  
Keyword(s):  
Time Trend ◽  
Ross Sea ◽  
Ice Core ◽  
Ice Cores ◽  
West Antarctica ◽  
Climatic Fluctuations ◽  
Long Time ◽  
Long Term Trends ◽  
Isotopic Records

A comparison is made of the Holocene records obtained from water isotope measurements along 11 ice cores from coastal and central sites in east Antarctica (Vostok, Dome B, Plateau Remote, Komsomolskaia, Dome C, Taylor Dome, Dominion Range, D47, KM105, and Law Dome) and west Antarctica (Byrd), with temporal resolution from 20 to 50 yr. The long-term trends possibly reflect local ice sheet elevation fluctuations superimposed on common climatic fluctuations. All the records confirm the widespread Antarctic early Holocene optimum between 11,500 and 9000 yr; in the Ross Sea sector, a secondary optimum is identified between 7000 and 5000 yr, whereas all eastern Antarctic sites show a late optimum between 6000 and 3000 yr. Superimposed on the long time trend, all the records exhibit 9 aperiodic millennial-scale oscillations. Climatic optima show a reduced pacing between warm events (typically 800 yr), whereas cooler periods are associated with less-frequent warm events (pacing >1200 yr).

scholarly journals Variability in accumulation rates from GPR profiling on the West Antarctic plateau

2004 ◽  
Vol 39 ◽  
pp. 238-244 ◽  
Author(s):  
Vandy B. Spikes ◽  
Gordon S. Hamilton ◽  
Steven A. Arcone ◽  
Susan Kaspari ◽  
Paul A. Mayewski
Keyword(s):  
Accumulation Rate ◽  
Ice Core ◽  
Ice Cores ◽  
Track Length ◽  
Flow Profile ◽  
Accumulation Rates ◽  
West Antarctica ◽  
West Antarctic ◽  
Ground Penetrating ◽  
Along Track

AbstractIsochronal layers in firn detected with ground-penetrating radar (GPR) and dated using results from ice-core analyses are used to calculate accumulation rates along a 100 km across-flow profile in West Antarctica. Accumulation rates are shown to be highly variable over short distances. Elevation measurements from global positioning system surveys show that accumulation rates derived from shallow horizons correlate well with surface undulations, which implies that wind redistribution of snow is the leading cause of this variability. Temporal changes in accumulation rate over 25–185 year intervals are smoothed to along-track length scales comparable to surface undulations in order to identify trends in accumulation that are likely related to changes in climate. Results show that accumulation rates along this profile have decreased in recent decades, which is consistent with core-derived time series of annual accumulation rates measured at the two ends of the radar profile. These results suggest that temporal variability observed in accumulation-rate records from ice cores and GPR profiles can be obscured by spatial influences, although it is possible to resolve temporal signals if the effects of local topography and ice flow are quantified and removed.

scholarly journals Recent climate variability around the Kerguelen Islands (Southern Ocean) seen through weather regimes

2021 ◽  
Author(s):  
Benjamin Pohl ◽  
Thomas Saucède ◽  
Vincent Favier ◽  
Julien Pergaud ◽  
Deborah Verfaillie ◽  
...  
Keyword(s):  
Climate Variability ◽  
Southern Ocean ◽  
Sea Water ◽  
Southern Oscillation ◽  
Surface Wind ◽  
Southern Annular Mode ◽  
Weather Regimes ◽  
Kerguelen Islands ◽  
Recent Climate

AbstractDaily weather regimes are defined around the Kerguelen Islands (Southern Ocean) based on daily 500 hPa geopotential height anomalies derived from the ERA5 ensemble reanalysis over the period 1979-2018. Ten regimes are retained as significant. Their occurrences are highly consistent across reanalysis ensemble members. Regimes show weak seasonality and non-significant long-term trends in their occurrences. Their sequences are usually short (1-3 days), with extreme persistence values above 10 days. Seasonal regime frequency is mostly driven by the phase of the Southern Annular Mode over Antarctica, mid-latitude dynamics over the Southern Ocean like the Pacific South American mode, and to a lesser extent, tropical variability, with significant but weaker relationships with El Niño Southern Oscillation. At the local scale over the Kerguelen Islands, regimes have a strong influence on measured atmospheric and oceanic variables, including minimum and maximum air temperature, mostly driven by horizontal advections, sea water temperature recorded 5 m below the surface, wind speed and sea level pressure. Relationships are weaker for precipitation amounts. Regimes also modify regional contrasts between observational sites in Kerguelen, highlighting strong exposure contrasts. The regimes allow improving our understanding of weather and climate variability and interactions in this region; they will be used in future work to assess past and projected long-term circulation changes in the southern mid-latitudes.

scholarly journals Accumulation variability derived from an ice core from coastal Dronning Maud Land, Antarctica

2004 ◽  
Vol 39 ◽  
pp. 339-345 ◽  
Author(s):  
Marzena Kaczmarska ◽  
Elisabeth Isaksson ◽  
Lars Karlöf ◽  
Jan-Gunnar Winther ◽  
Jack Kohler ◽  
...  
Keyword(s):  
High Resolution ◽  
Accumulation Rate ◽  
Ice Core ◽  
Austral Summer ◽  
Conductivity Measurement ◽  
Ice Cores ◽  
Electrical Conductivity Measurement ◽  
Regional Pattern ◽  
Dronning Maud Land

AbstractA 100 m long ice core was retrieved from the coastal area of Dronning Maud Land (DML), Antarctica, in the 2000/01 austral summer. The core was dated to AD 1737 by identification of volcanic horizons in dielectrical profiling and electrical conductivity measurement records in combination with seasonal layer counting from high-resolution oxygen isotope (δ18O) data. A mean long-term accumulation rate of 0.29 ma–1w.e. was derived from the high-resolution δ18O record as well as accumulation rates during periods in between the identified volcanic horizons. A statistically significant decrease in accumulation was found from about 1920 to the present. A comparison with other coastal ice cores from DML suggests that this is a regional pattern.

scholarly journals A debris-covered glacier at Kerguelen (49°S, 69°E) over the past 15 000 years

2020 ◽  
pp. 1-13
Author(s):  
Joanna Charton ◽  
Vincent Jomelli ◽  
Irene Schimmelpfennig ◽  
Deborah Verfaillie ◽  
Vincent Favier ◽  
...  
Keyword(s):  
Climate Variability ◽  
Late Holocene ◽  
Ice Cores ◽  
Cosmic Ray ◽  
Late Glacial ◽  
Temperature Changes ◽  
Precipitation Changes ◽  
The Antarctic ◽  
Exposure Ages

Abstract Debris-covered glaciers constitute a large part of the world's cryosphere. However, little is known about their long-term response to multi-millennial climate variability, in particular in the Southern Hemisphere. Here, we provide first insights into the response of a debris-covered glacier to multi-millennial climate variability in the sub-Antarctic Kerguelen Archipelago, which can be compared to that of recently investigated debris-free glaciers. We focus on the Gentil Glacier and present 13 new 36Cl cosmic-ray exposure ages from moraine boulders. The Gentil Glacier experienced at least two glacial advances: the first one during the Late Glacial (19.0–11.6 ka) at ~14.3 ka and the second one during the Late Holocene at ~2.6 ka. Both debris-covered and debris-free glaciers advanced broadly synchronously during the Late Glacial, most probably during the Antarctic Cold Reversal event (14.5–12.9 ka). This suggests that both glacier types at Kerguelen were sensitive to abrupt temperature changes recorded in Antarctic ice cores, associated with increased moisture. However, during the Late Holocene, the advance at ~2.6 ka was not observed in other glaciers and seems to be an original feature of the debris-covered Gentil Glacier, related to either distinct dynamics or to distinct sensitivity to precipitation changes.

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